board/raspberrypi/post-image.sh: pass an empty rootpath to genimage

genimage makes a full copy of the given rootpath to ${GENIMAGE_TMP}/root
so passing TARGET_DIR would be a waste of time and disk space. We don't
rely on genimage to build the rootfs image, just to insert a pre-built
one in the disk image.

Signed-off-by: Carlos Santos <unixmania@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

board/raspberrypi/post-image.sh

@@ -49,10 +49,18 @@ __EOF__
 
 done
 
+# Pass an empty rootpath. genimage makes a full copy of the given rootpath to
+# ${GENIMAGE_TMP}/root so passing TARGET_DIR would be a waste of time and disk
+# space. We don't rely on genimage to build the rootfs image, just to insert a
+# pre-built one in the disk image.
+
+trap 'rm -rf "${ROOTPATH_TMP}"' EXIT
+ROOTPATH_TMP="$(mktemp -d)"
+
 rm -rf "${GENIMAGE_TMP}"
 
-genimage                           \
-	--rootpath "${TARGET_DIR}"     \
+genimage \
+	--rootpath "${ROOTPATH_TMP}"   \
 	--tmppath "${GENIMAGE_TMP}"    \
 	--inputpath "${BINARIES_DIR}"  \
 	--outputpath "${BINARIES_DIR}" \